Structure of β-uranium

Lawson, A. C.; Olsen, C.E.; Richardson, J. W.; Mueller, Matthias; Lander, G. H.

doi:10.1107/s0108768187009406

Cited by 102 publications

(65 citation statements)

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“…Also, for both structures, the calculated lattice parameter ratio c/a (0.523, 1.978, and 1.792 for0020β-uranium, distorted A15, and hexagonal, resp.) is in reasonable accord with the previously considered data (0.531, 1.860, and 1.890, [1,7,[28][29][30][31] and 1.098 for TaZrNO that is also in reasonable accord with of 1.064) [27]. In order to attempt an understanding the interatomic distances of the various compounds, we have found excellent agreement between our calculated and available experiment interatomic distances for different phases of pure tantalum.…”

Section: Structural Propertiessupporting

confidence: 89%

Structural and Electronic Properties of Pure Ta, TaNO, and TaZrNO with Ab Initio Calculations

et al. 2012

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This paper presents the results of self-consistent first-principle calculations for the crystal structure and electronic structure of pure tantalum, TaNO, and TaZrNO within density functional theory (DFT) for the sake of comparison and shows the influence of allowing elements on the interatomic distance and the Fermi level. The large total densities of states (TDOS) value for TaZrNO implies the highest electronic conductivity. The difference in values is due to the Zr metallic atoms presence in TaZrNO

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Section: Structural Propertiessupporting

confidence: 89%

Structural and Electronic Properties of Pure Ta, TaNO, and TaZrNO with Ab Initio Calculations

et al. 2012

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“…In the 1950s Frank and Kasper (3,4) recognized complex tetrahedral atomic-and molecular-packing geometries that bridge the familiar close-packed crystals [e.g., face-centered cubic (FCC), hexagonally close-packed (HCP), and body-centered cubic (BCC) structures] characterized by periodic order, and quasiperiodic crystals (QCs) that extend crystallography beyond the 230 space groups relevant to periodic crystals (5,6). The scientific literature is replete with examples of Frank-Kasper phases in hard materials, particularly in the area of intermetallics (7)(8)(9), but also in a few complex elemental crystals, including manganese (10,11) and uranium (12). Recently, this class of crystalline order has cropped up in a host of soft materials, including dendrimers (13), surfactant solutions (14), and block polymers (15,16), often in close proximity to QC phases (17)(18)(19).…”

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confidence: 99%

Sphericity and symmetry breaking in the formation of Frank–Kasper phases from one component materials

Lee

Leighton

Bates

2014

Proc. Natl. Acad. Sci. U.S.A.

223

362

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Frank-Kasper phases are tetrahedrally packed structures occurring in numerous materials, from elements to intermetallics to selfassembled soft materials. They exhibit complex manifolds of Wigner-Seitz cells with many-faceted polyhedra, forming an important bridge between the simple close-packed periodic and quasiperiodic crystals. The recent discovery of the Frank-Kasper σ-phase in diblock and tetrablock polymers stimulated the experiments reported here on a poly(isoprene-b-lactide) diblock copolymer melt. Analysis of small-angle X-ray scattering and mechanical spectroscopy exposes an undiscovered competition between the tendency to form self-assembled particles with spherical symmetry, and the necessity to fill space at uniform density within the framework imposed by the lattice. We thus deduce surprising analogies between the symmetry breaking at the body-centered cubic phase to σ-phase transition in diblock copolymers, mediated by exchange of mass, and the symmetry breaking in certain metals and alloys (such as the elements Mn and U), mediated by exchange of charge. Similar connections are made between the role of sphericity in real space for polymer systems, and the role of sphericity in reciprocal space for metallic systems such as intermetallic compounds and alloys. These findings establish new links between disparate materials classes, provide opportunities to improve the understanding of complex crystallization by building on synergies between hard and soft matter, and, perhaps most significantly, challenge the view that the symmetry breaking required to form reduced symmetry structures (possibly even quasiperiodic crystals) requires particles with multiple predetermined shapes and/or sizes.symmetry breaking | sphericity | Frank-Kasper phases | block polymers T he discovery of materials with aperiodic order, often referred to as "quasicrystals," 30 years ago (1, 2) heralded new and promising vistas for designing materials endowed with unique properties. In the 1950s Frank and Kasper (3, 4) recognized complex tetrahedral atomic-and molecular-packing geometries that bridge the familiar close-packed crystals [e.g., face-centered cubic (FCC), hexagonally close-packed (HCP), and body-centered cubic (BCC) structures] characterized by periodic order, and quasiperiodic crystals (QCs) that extend crystallography beyond the 230 space groups relevant to periodic crystals (5, 6). The scientific literature is replete with examples of Frank-Kasper phases in hard materials, particularly in the area of intermetallics (7-9), but also in a few complex elemental crystals, including manganese (10, 11) and uranium (12). Recently, this class of crystalline order has cropped up in a host of soft materials, including dendrimers (13), surfactant solutions (14), and block polymers (15, 16), often in close proximity to QC phases (17)(18)(19). To the best of our knowledge the principles underlying the formation of Frank-Kasper phases across both categories of materials have not been established, presenting enticing challenges to sc...

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“…This transformation is perhaps associated to a phase transition between 973 and 1030 K. At 1030 K, β-U can be described with the same composite symmetry as β-Ta at 15 K (table I). Experimental powder diffraction data of β-U [7] cannot exclude a possible incommensurate structure. Therefore at 1030 K [7], β-U is a commensurate or incommensurate two-component composite similar to β-Ta.…”

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confidence: 99%

“…Experimental powder diffraction data of β-U [7] cannot exclude a possible incommensurate structure. Therefore at 1030 K [7], β-U is a commensurate or incommensurate two-component composite similar to β-Ta.…”

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confidence: 99%

“…-We postulate that every Frank-Kasper σ-structure tends to have a two-component composite structure (commensurate or incommensurate) under some specific P -T conditions. For instance, our brief analysis of the β-U interatomic distances based on structural data obtained at 955, 973 and 1030 K [7] indicates important similarities with β-Ta. The unusually short U-U bonds observed in the G-chains and in the plane of the H-net give rise to the formation of clusters.…”

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confidence: 99%

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Atomic clusters and phase transitions in the metastable β-Ta phase between 4.2 and 293 K

Arakcheeva

Chapuis

2005

Europhys. Lett.

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Atomic clusters were identified in the ground state of the non-equilibrium Ta phase (Frank-Kasper σ-structure type) at 15, 120 and 293 K. The evolution of the clusters with temperature leads to two phase transformations at 65 and 150 K which are related to the electrical and magnetic properties. The magnetic phase transition at 65 K is associated with the magnetic symmetry group transformation P 4 2 /mn m (< 65 K) to P 4 (> 65 K). It is shown that β-U is also a two-component composite containing similar clusters. The nature of the stabilisation of β-Ta at the cathode is discussed.

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Structure of β-uranium

Cited by 102 publications

References 4 publications

Structural and Electronic Properties of Pure Ta, TaNO, and TaZrNO with Ab Initio Calculations

Structural and Electronic Properties of Pure Ta, TaNO, and TaZrNO with Ab Initio Calculations

Sphericity and symmetry breaking in the formation of Frank–Kasper phases from one component materials

Atomic clusters and phase transitions in the metastable β-Ta phase between 4.2 and 293 K

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